In known TDMA systems, a predetermined series of time segments of a transmission channel is allocated to the transmission of a particular data signal. The allocation of time segments of the channel is independent of the timing of the data input. It is also known to provide a queue of signals awaiting transmission and to provide that more urgent data may jump to the front of the queue for transmission using the next available allocated time segment.
For certain types of data communication there is a need to reduce as far as possible the transmission delay, for example for a two way speech or video transmission. A problem with existing TDMA systems is that delays may arise between the preparation of data packets for transmission and the availability of allocated time segments for that data.